The long term objectives of this project are to analyse the respiratory system of E. coli through a combination of genetic and biochemical studies of mutants defective in electron transport and oxidative phosphorylation. The most promising means of isolating such mutants is through their resistance to antibiotics such as neomycin, streptomycin and other aminoglycosides and their loss of the ability to grow on one or more non-fermentable carbon sources. Our primary attention has been and will continue to be directed to the study of mutants with defects in electron transport. Our aim is to determine the number of components involved and their interaction patterns. Because of the severe overlap of cytochrome absorption bands, special techniques such as low-temperature difference spectroscopy and numerical analysis of spectra are required to even identify such mutants.